Display device

ABSTRACT

A display device includes: a display functional layer that can change display for each pixel in accordance with an application voltage; a plurality of driving electrodes separately disposed in one direction; a plurality of pixel signal lines to which pixel signals used for applying the application voltage to the display functional layer in accordance with an electric potential difference from the display reference electric potential are applied; a plurality of detection electrodes that are separately disposed in a direction other than the one direction, are coupled with the driving electrodes as electrostatic capacitance, generate detection electric potentials in response to the detection driving signal, and change the detection electric potential in accordance with approach of a detection target object; and a pixel signal control unit that controls the pixel signals so as to include pixel signals having different polarities during the display period.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation application of U.S.Application No. 12/820,685, filed Jun. 22, 2010, which applicationclaims priority to Japanese Priority Patent Application JP 2009-155201filed in the Japan Patent Office on Jun. 30, 2009, the entire content ofwhich is hereby incorporated by reference.

BACKGROUND

The present application relates to a sensor built-in display device inwhich an electrode, to which a driving signal of sensor detection isapplied, is additionally used as an electrode to which a displayreference electric potential is applied.

Contact detecting devices that are so-called touch panels are known. Thetouch panels, that are formed so as to be overlapped with a displaypanel, allow information input replacing ordinary buttons by displayingvarious buttons as an image on a display surface. When this technologyis applied to small-sized mobile devices, disposition of display anddisposition of buttons can be commonly used. Accordingly, a significantadvantage of enlarging the screen, saving the space of an operationunit, or a decrease in the number of components is acquired.

As described above, generally a “touch panel” represents a contactdetecting device having a panel shape that is built in the displaydevice.

However, when the touch panel is arranged on a liquid crystal panel, theentire thickness of a liquid crystal module is increased. Thus, forexample, in Japanese Unexamined Patent Application Publication No.2008-9750, a liquid crystal display device, to which an electrostaticcapacitive-type touch panel is added, having a structure appropriate fordecreasing the thickness is proposed.

An electrostatic capacitive-type touch sensor has a plurality of drivingelectrodes and a plurality of detection electrodes that formelectrostatic capacitance together with the plurality of drivingelectrodes. The detection precision of a sensor is in proportion to thenumber of the driving electrodes and the detection electrodes. However,in a case where sensor output lines are arranged in addition to thedetection electrodes, the number of wirings becomes vast. Accordingly,in order to allow detection electrodes to function as sensor outputlines, a driving method in which one of the plurality of drivingelectrodes is AC driven, and the driving electrode that is AC driven isshifted in a direction (hereinafter, referred to as a scanningdirection), in which the driving electrodes are aligned at a constantpitch, becomes a mainstream. In a case where a technique of scanning thedriving electrodes that are AC driven in one direction is used, when anelectric potential change of the detection electrode is observed infollow-up of the scanning, contact or proximity of a detection targetobject to the touch panel surface can be detected based on the scanningposition in which an electric potential change occurs.

SUMMARY

In a case where such a touch panel is applied to a display device, whenthe entire device is formed to be thin, the AC-driven driving electrodecan easily interfere electrically with signal lines and electrodes,which are used for display driving, for detection driving.

There are cases where the signal lines and the electrodes, which areused for display driving, are driven due to application of pixel signalsto the signal lines and the electrodes for display or AC inversion ofthe electric potential reference (display reference electric potential)of a display voltage applied to a display functional layer such as aliquid crystal layer. Accordingly, there are cases where the change inthe electric potential for such display causes the electric potential ofthe detection electrode to fluctuate through the driving electrode andbecomes a noise source in object detection.

In particular, there are cases where the display reference electricpotential of the display functional layer is driven in an AC inversionmanner, and an extreme grayscale display is performed such as the caseof white display or black display by using a pixel signal that uses thedisplay reference electric potential that is driven in the AC inversionmanner as a reference. In such cases, there are cases where the DCelectric potential level of the detection electrode is changed under theinfluence of the pixel signal so as to be a noise at the time ofdetection, and such a change blocks high-precision objection detection.In addition, there are cases where the detection precision is lowereddepending on a force of interference between the electrodes in halftonegrayscale display other than the white display and the black display.

It is desirable to provide a touch sensor-built-in display devicecapable of preventing or suppressing a decrease in the precision ofobject detection due to pixel signals.

According to an embodiment, there is provided a display device includinga display functional layer, a plurality of driving electrodes, aplurality of pixel signal lines, a plurality of detection electrodes,and a pixel signal control unit.

The display functional layer is configured so as to change display foreach pixel in accordance with an application voltage.

The plurality of driving electrodes are disposed in one direction so asto be separated from one another, and to the plurality of drivingelectrodes, a constant display reference electric potential is appliedduring a display period in which display is performed in a pixelarrangement along the one direction and a detection driving signal isapplied when detection scanning is performed by changing the displayreference electric potential to another electric potential.

To the plurality of pixel signal lines, pixel signals used for applyingthe application voltage to the display functional layer in accordancewith an electric potential difference from the display referenceelectric potential are applied.

The plurality of detection electrodes are disposed so as to be separatedfrom one another in a direction other than the one direction, arecoupled with the plurality of the driving electrodes as electrostaticcapacitance, generate detection electric potentials in response to thedetection driving signal, and change the detection electric potential inaccordance with approach of a detection target object.

The pixel signal control unit controls the plurality of pixel signalsapplied to the plurality of pixel signal lines so as to include pixelsignals having different polarities during the display period.

Under the above-described configuration, the detection scanning is notperformed during the fixed display period. Accordingly, a fixed displayreference electric potential is applied to the plurality of drivingelectrodes. Then, under the control of the pixel signal control unit,during the display period, a plurality of pixel signals applied to theplurality of pixel signal lines include pixel signals having differentpolarities. Accordingly, changes in the electric potentials of theplurality of pixel signal lines are offset at the ratio of inclusion ofthe pixel signals having different polarities. Accordingly, even in acase where each driving electrode is electrically coupled with theplurality of pixel signal lines, the electric potential of the drivingelectrode is not changed due to the pixel signal or the change in theelectric potential is suppressed. As a result, the change in theelectric potential of the detection electrode that is capacitivelycoupled with each driving electrode due to the pixel signal, that is, anoise component of object detection is prevented or suppressed.

According to an embodiment, a touch sensor built-in display devicecapable of preventing or suppressing a decrease in the precision ofobject detection due to pixel signals can be provided.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A to 1D are plan views specialized for the disposition ofelectrodes of a display device according to an embodiment and circuitsused for driving the electrodes and detection.

FIG. 2 is an equivalent circuit diagram of a pixel.

FIG. 3 is a plan view representing a top view of a TFT substrate of apixel of an FFS liquid crystal.

FIG. 4 is a block diagram showing a configuration example of a driverthat can perform dot inversion for inverting the polarity of a pixelsignal for each pixel.

FIG. 5 is a plan view showing the configuration for performing matrixdriving of a pixel arrangement that is colored for each pixel by using asource line and a gate line.

FIGS. 6A and 6B are diagrams illustrating the common electric potentialand the polarity of a pixel signal in a six-selector mode.

FIGS. 7A and 7B are diagrams showing the polarities of pixel signalpulses corresponding to a measurement result of a change in the electricpotential of a detection electrode (sensor line) according to acomparative example in which 1 H Vcom inversion driving is performed.

FIGS. 8A and 8B are diagrams representing the polarity of error and thepath of a change in the electric potential of a sensor line.

FIGS. 9A and 9B are diagrams representing a common electric potentialand a pixel signal according to the first embodiment.

FIGS. 10A and 10B are diagrams illustrating the effect of the firstembodiment.

FIGS. 11A and 11B are diagrams showing the relationship between a commonelectric potential and a pixel signal according to the secondembodiment.

FIG. 12 is a diagram illustrating a method of defining two areas (or twopixels forming a pixel pair) within one pixel.

FIG. 13 is a schematic diagram of a cross-section structure showing afirst modified example of the configuration of a liquid crystal displaydevice of the horizontal electric field mode.

FIG. 14 is a schematic diagram of a cross-section structure showing asecond modified example of the configuration of a liquid crystal displaydevice of the horizontal electric field mode.

FIG. 15 is a schematic diagram of a cross-section structure showing athird modified example of the configuration of a liquid crystal displaydevice of the horizontal electric field mode.

DETAILED DESCRIPTION

The present application will be described in detail below with referenceto the drawings according to an embodiment.

1. First Embodiment

This is an embodiment in which pixel signals having different polaritiesare included within 1 H period. As a preferred embodiment, a case wherethe polarity is alternately inverted is described as an example.

2. Second Embodiment

This is an embodiment representing an example of driving two areas (ortwo pixels that form a pixel pair) within one pixel by using a samepixel signal.

3. Modified Examples 1. First Embodiment

Basic Configuration of Display Device

FIGS. 1A to 1C show plan views specialized for the disposition ofelectrodes of a display device according to this embodiment and circuitsused for driving the electrodes or detection. In addition, FIG. 1D showsa schematic cross-sectional structure of the display device according tothis embodiment. FIG. 1D shows a cross-section of six pixels, forexample, arranged in a row direction (the direction of a pixel displayline). FIG. 2 is an equivalent circuit diagram of a pixel.

The display device shown in FIGS. 1A to 1D is a liquid crystal displaydevice that includes a liquid crystal layer as a “display functionallayer”.

The liquid crystal display device has an electrode common to a pluralityof pixels and an electrode (driving electrode) to which a commonelectric potential Vcom, which provides a reference voltage of signalvoltages used for grayscale display of each pixel, is applied on theside of one substrate of two substrate elements opposing each other withthe liquid crystal layer interposed therebetween.

In FIG. 1D, in order to allow the structure of the cross-section to beeasily viewed, a driving electrode, and a pixel electrode, and adetection electrode that are major configurations of this embodiment arehatched, and other portions (substrates, an insulating film, afunctional layer, and the like) are not hatched. The not hatching of theother portions are the same in other structural diagrams of thecross-section described later.

In the liquid crystal display device 1, pixels PIX shown in FIG. 2 aredisposed in a matrix pattern. Each pixel PIX, as shown in FIG. 2, has athin film transistor (TFT; hereinafter denoted by TFT 23) as a selectiondevice of a pixel, an equivalent capacitor C6 of the liquid crystallayer 6, and a retention capacitor (additional capacitance) Cx. Oneelectrode of the equivalent capacitance C6 representing the liquidcrystal layer 6 is a pixel electrode 22 that is disposed in the matrixpattern so as to be separated for each pixel, and the other electrode isa driving electrode 43 that is common to a plurality of pixels.

The pixel electrode 22 is connected to one of the source and the drainof the TFT 23, and a pixel signal line (hereinafter, referred to as asource line SL) is connected to the other of the source and the drain ofthe TFT 23. The source line SL is connected to a vertical drivingcircuit (source driver) to be described later, and a pixel signal issupplied to the source line SL from the vertical driving circuit.

The gate of the TFT 23 is configured to be electrically common to allthe pixels PIX aligned in the row direction, that is, the horizontaldirection of a display screen, and whereby a display scanning line isformed. A gate pulse that is output from the vertical driving circuitnot shown in the figure and is used for opening or closing the gate ofthe TFT 23 is supplied to the display scanning line, and thus, thedisplay scanning line is referred to as a gate line GL hereinafter.

As shown in FIG. 2, the retention capacitor Cx is connected to theequivalent capacitor C6 in a parallel manner. The equivalent capacitanceC6 has insufficient accumulation capacitance. Thus, the retentioncapacitor Cx is disposed so as to prevent a decrease in the writeelectric potential due to a leakage current of the TFT 23 or the like.In addition, the addition of the retention capacitor Cx also contributesto prevention of flicker and improvement of uniformity in screenluminance.

When viewed from the cross-sectional structure (FIG. 1D), the liquidcrystal display device 1 has a substrate (hereinafter, referred to as adriving substrate 2) in which the TFT 23 shown in FIG. 2 is formed in anarea not shown in the cross-section and to which a pixel driving signal(pixel signal voltage) is supplied. In addition, the liquid crystaldisplay device 1 includes an opposing substrate 4 disposed so as to facethe driving substrate 2 and a liquid crystal layer 6 interposed betweenthe driving substrate 2 and the opposing substrate 4.

The driving substrate 2 includes a TFT substrate 21 (a substrate bodyportion is formed from glass or the like) as a circuit substrate inwhich the TFT 23 shown in FIG. 2 is formed, a driving electrode 43 thatis formed on the TFT substrate 21, and a plurality of pixel electrodes22. The plurality of pixel electrodes 22, although not shown in FIGS. 1Ato 1D, includes the plurality of pixel electrodes 22 that are disposedin a matrix pattern.

In the TFT substrate 21, a display driver (see FIG. 4 to be describedlater), not shown in the figure, used for driving each pixel electrode22 is formed. In addition, in the TFT substrate 21, the TFT 23 and wiressuch as the source line SL and the gate line GL, which are shown in FIG.2, are formed. A contact detecting unit 8 may be formed in the TFTsubstrate 21.

The opposing substrate 4 includes a glass substrate 41, a color filter42 that is formed on one surface of the glass substrate 41, and adriving electrode 43 that is formed on the color filter 42 (the liquidcrystal layer 6 side). The color filter 42 is configured by periodicallyarranging color filter layers, for example, of three colors of red (R),green (G), and blue (B), and one of the three colors of R, G, and B isassigned to each pixel PIX (the pixel electrode 22). There are caseswhere a pixel to which one color is assigned is referred to as a subpixel, and sub pixels of three colors of R, G, and B are referred to asa pixel. However, here, such a sub pixel is also denoted by a pixel PIX.

The driving electrode 43 is used also as a driving electrode DE of atouch detecting sensor that configures a part of a touch sensorperforming a touch detecting operation.

To the driving electrode 43, a fixed common electric potential Vcom as areference electric potential of a pixel voltage that is supplied to thepixel electrode 22 so as to apply an electric field to the liquidcrystal layer 6 is applied. On the other hand, the driving electrode 43is used also as the driving electrode DE of the touch detecting sensor.Accordingly, an AC pulse signal supplied from an AC signal source ASshown in FIGS. 1A to 1D is applied to the driving electrode 43 whentouch detecting scanning is performed.

On the other surface (the display surface side) of the glass substrate41, a sensor line SNL is formed. In addition, on the sensor line SNL, aprotection layer 45 is formed. The sensor line SNL configures a part ofthe touch sensor and corresponds to the detection electrode E2 shown inFIGS. 1A to 1D and 2. The sensor line SNL is formed from a transparentelectrode material such as ITO, IZO, or an organic conductive film. Inaddition, in the glass substrate 41, the contact detecting unit 8 thatperforms a touch detecting operation may be formed.

The liquid crystal layer 6 as a “display functional layer” modulateslight passing through it in the thickness direction (a direction inwhich electrodes face each other) in accordance with the state of anapplied electric field. As the material of the liquid crystal layer 6,liquid crystal materials of various modes such as a TN (twisted nematic)mode, a VA (Vertical Alignment) mode, and an ECB (ElectricallyControlled Birefringence) mode.

In addition, between the liquid crystal layer 6 and the drivingsubstrate 2 and between the liquid crystal layer 6 and the opposingsubstrate 4, alignment films are disposed. In addition, on the surfaceof the driving substrate 2 (that is, the rear surface side) opposite tothe display surface and the display surface side of the opposingsubstrate 4, polarizing plates are disposed. Such optical functionallayers are not shown in FIG. 3.

In addition, n sensor lines SNL1 to SNLn correspond to a “plurality ofdetection electrodes” according to an embodiment. The n sensor linesSNL1 to SNLn, as shown in FIG. 1A are formed from a plurality of wireselongated in the direction y. Hereinafter, arbitrary one of the sensorlines SNL1 to SNLn is denoted by a sensor line

The driving electrode 43 shown in FIG. 1D corresponds to each of kmdriving electrodes shown in FIG. 1A.

Each driving electrode is formed in a band shape that is elongated inthe direction x, and km driving electrodes are disposed at a same pitchin the direction y. Each of a driving electrode group DEj (j=1, 2, 3, .. . , m), which is simultaneously driven, is configured by k drivingelectrodes 43 among these. Each driving electrode 43 is disposed in adirection different from that of n sensor lines SNL1 to SNLn. In thisexample, the driving electrode DEj and the sensor line SNLi are disposedso as to be perpendicular to each other.

The pitch of the divided dispositions of driving electrodes 43-1 to43-km that are divided into (k×m) parts is set to a value that is(natural number) times the (sub) pixel pitch or the disposition pitch ofthe pixel electrodes. Here, the pitch of the divided dispositions of thedriving electrodes is assumed to be the same as the disposition pitch ofthe pixel electrodes.

The reason for performing AC driving in units of k driving electrodes DEis so as to set the unit of the AC driving to be larger than one pixelline and increase the electrostatic capacitance of the touch sensor forincreasing the detection sensitivity. In addition, invisibility of shiftcan be achieved by shifting the driving electrodes DE by (naturalnumber) times the pixel pitch unit.

The materials of the TFT substrate 21 and the glass substrate 41 shownin FIG. 1B are not particularly limited. However, it is necessary thateach (SLi) of the n sensor lines SNL1 to SNLn and each (DEj) of the mdriving electrodes DE1 to DEm are capacitively coupled. Accordingly, thethickness and the material of the glass substrate 41 are regulated inthe viewpoint of allowing the capacitive coupling to have apredetermined force.

As shown in FIG. 1A, a driving control unit 9 is disposed so as to beconnected to one end of each of the m driving electrodes DE1 to DEm. Inaddition, a contact detecting unit 8 is disposed to one end of each ofthe n sensor lines SNL1 to SNLn.

In addition, the contact detecting unit 8 may be disposed on the outsideof the liquid crystal display device 1. However, in this example, thecontact detecting unit 8 is built in the liquid crystal display device1.

The driving control unit 9 has an AC signal source AS for each drivingelectrode. The driving control unit 9 is a circuit that changes anactivated AC signal source AS in a direction (scanning direction)denoted by an arrow represented within the block of the driving controlunit 9 shown in FIG. 1A. Alternatively, the driving control unit 9 maybe a circuit that has one AC signal source AS and switches a connectionbetween the one AC signal source AS and one of the m driving electrodesin the scanning direction.

The driving control unit 9 is a circuit that performs detection scanningdriving.

Here, the “detection scanning driving” is an operation of performing anoperation of applying a detection driving voltage (for example, an ACvoltage) and a shift operation of shifting between application targetsin one direction (a first direction; here the direction y). A detectiondriving voltage (AC pulse signal) is applied, for example, to thedriving electrode 43 (the driving electrode 43 may be one; however,here, k driving electrodes 43 that are adjacent to one another) to whicha fixed common electric potential Vcom is applied. The drivingelectrodes other than the driving electrodes to which the detectiondriving voltage is applied are maintained to a fixed common electrodepotential Vcom.

However, the applying of the detection driving voltage (AC pulse signal)for touch detection scanning is controlled not to be overlapped with apixel line for display scanning.

In other words, in the pixel line of the display scanning, the TFT 23 isturned on in accordance with activation of the gate line GL shown inFIG. 2, and a pixel signal of the source line SL is written into thepixel electrode 22. At that time, it is necessary to maintain theelectric potential of the driving electrode 43 at the fixed commonelectric potential Vcom, and thus, it is difficult to apply a detectiondriving voltage used for the touch detection scanning to the drivingelectrode 43.

The detection driving voltage for the touch detection scanning isapplied to the driving electrode 43 so as not to be overlapped with thedisplay scanning At this time, the detection driving voltage is appliedto a bundle of the driving electrodes 43 that is formed in units of thedriving electrodes DE. In addition, a shift operation may be performed,for example, in units of one or more pitches of the driving electrodes43 that is smaller than the width (it approximately corresponds to thepitch of the k driving electrodes 43) of the driving electrode DE. Thisis for implementing invisibility, so that it becomes difficult tovisually recognize shifting between the driving electrodes DE. Theapplication of the detection driving voltage and the shift operationthereof are performed by the driving control unit 9, for example, undercontrol of the control unit not shown in the figure in accordance with apredetermined algorithm.

Since each of the n sensor lines SNL1 to SNLn is capacitively coupledwith the km driving electrodes 43, the pulse of the detection drivingvoltage that is applied to the driving electrode 43 is delivered throughthe electrostatic capacitance. Accordingly, a change in the electricpotential occurs in each sensor, and the crest value changes (commonlydecreases) as a detection target object (a person's fingertip or thelike) approaches the outside thereof. The detection circuit DET of thecontact detecting unit 8 detects placement of the detection targetobject when the change in the electric potential becomes a predeterminedmagnitude.

In addition, FIGS. 1A and 1B are diagrams for separately illustratingelectrode patterns. However, actually, as shown in FIG. 1C, the drivingelectrodes 43-1 to 43-km and the sensor lines SNLi are disposed in anoverlapping manner.

Under such a configuration, the contact detecting unit 8 can detect theposition for the row direction based on the detection circuit DET inwhich a voltage change occurs and can acquire the position for thecolumn direction based on the timing at the time of detection. In otherwords, it is assumed that scanning of the driving control unit 9 for thedetection driving voltage and the operation of the contact detectingunit 8 are synchronized, for example, with a clock signal having apredetermined cycle. By performing such a synchronization operation, thedriving electrode that is driven by the driving control unit 9 when thevoltage change is acquired by the contact detecting unit 8 can beidentified. Accordingly, the center of the contact position of thefinger can be detected. Such a detection operation is controlled by anoverall control circuit of a computer base, not shown in the figure,such as a CPU, a microcomputer, or a control circuit for touch detectionthat controls the overall operation of the liquid crystal display device1.

The driving control unit 9 is formed on the driving substrate 2 side inFIG. 1D. However, the contact detecting unit 8 may be disposed on thedriving substrate 2 side, the opposing substrate 4, or the outside ofthe liquid crystal display device 1.

Since many TFTs are integrated, it is desirable to form the contactdetecting unit 8 in the driving substrate 2 in order to decrease thenumber of manufacturing processes. However, there are cases where thesensor lines SNL formed from a transparent electrode material are placedon the opposing substrate 4 side and the wiring resistance increases. Insuch a case, in order to avoid the inconvenience of high wiringresistance, it is preferable to form the contact detecting unit 8 on theopposing substrate 4 side. However, there is a disadvantage of highcosts in a case where a TFT forming process is used in the opposingsubstrate 4 only for the contact detecting unit 8. In consideration ofall the advantages and all the disadvantages described above, theformation position of the contact detecting unit 8 may be determined.

Liquid Crystal Driving in Horizontal Electric Field Mode

FIG. 3 shows a top view of a TFT substrate 21 of a pixel PIX of an FFS(Field Fringe Switching) mode liquid crystal.

A pixel electrode 22 is formed in a transparent electrode layer TE andhas a plurality of slits. As the material of the transparent electrode,an ITO, an IZO, an organic conductive film, or the like can be used. Onthe lower side of the pixel electrode 22, a driving electrode 43 isformed so as to face the pixel electrode 22 (FIG. 1D). The drivingelectrode 43 is formed in the transparent electrode layer TE that iscommon to all the pixels.

The pixel electrode 22 is connected to an internal wire 47, which isformed from aluminum AL or the like, of the lower layer through acontact 46. The internal wire 47 is connected to one of the source andthe drain that are formed in a thin film semiconductor layer 48 of a TFT23 that is formed from poly silicon (PS). To the other of the source andthe drain of the thin film semiconductor layer 48, a source line SL thatis formed from aluminum (AL) is connected. A gate line GL that isintersects a lower layer of the thin film semiconductor layer 48 isformed from a gate metal (GM) such as molybdenum (Mo) and is disposed ina direction perpendicular to the source line SL.

In addition, on the upper side (a portion not shown in the figure) ofthe TFT substrate 21 having various patterns shown in FIG. 3, theopposing substrate 4 shown in FIG. 1D is overlapped, and a liquidcrystal layer 6 is formed between the two layers. A first polarizingplate and a second polarizing plate are disposed on the two substrates.

Configuration of Display Driver

FIG. 4 is a block diagram showing a configuration example of a driverthat can perform dot inversion for inverting the polarity of a pixelsignal for each pixel.

The liquid crystal display device 1 shown in FIG. 4 has a display unit100 in which the pixels PIX shown in FIGS. 2 and 3 are arranged in amatrix pattern.

From the display unit 100, s source lines SL1 to SLs are drawn out fromone side of the direction y, and km gate lines GL1 to GLkm are drawn outfrom one side of the direction x.

To the s source lines SL1 to SLs, a source driver (S_DRV) 300 as a pixelsignal driving circuit is connected. In addition, to the km gate linesGL1 to GLkm, a gate driver (G_DRV) 400 is connected.

In addition, to the source driver 300 and the gate driver 400, a displaycontrol circuit (DIS_CONT) 200 that controls the drivers is connected.

For example, a “pixel signal control unit” according to an embodiment isconfigured by the source driver 300, the gate driver 400, and thedisplay control circuit 200.

To the display control circuit 200, a digital video signal Dv thatrepresents an image to be displayed and a control signal Dc that is usedfor controlling a display operation are input from an external signalsource. In addition, to the display control circuit 200, a horizontalsynchronization signal HSY and a vertical synchronization signal VSYcorresponding to the digital video signal Dv are externally supplied.

The display control circuit 200 generates four signals DA, Cch, SSP, andSCK of a source driving system and three signals GCK, GSP, and GOE of agate driving system as signals used for displaying an image representedby the digital video signal Dv in the display unit 100. The displaycontrol circuit 200 generates such signals based on the input signalsDv, Dc, HSY, and VSY.

Here, the digital pixel signal DA is a signal that is generated by thedisplay control circuit 200 based on the video signal Dv and includesdisplay grayscale information. The display control circuit 200 generatesa digital pixel signal DA by performing timing adjustment of the videosignal Dv in the internal memory or the like as is necessary and outputsthe digital pixel signal DA to the source driver 300.

In addition, the display control circuit 200 generates a data startpulse signal SSP, a data clock signal SCK, and a short circuit controlsignal Csh and outputs the generated signals to the source driver 300.

The data clock signal SCK is a signal formed from pulses correspondingto each pixel of an image represented by the digital pixel signal DA andis used as a shift operation clock of the source driver 300.

The data clock signal SCK is a signal that is in the high level (levelH) only for a predetermined period for each one horizontal scanningperiod (1 H) based on the horizontal synchronization signal HSY and is asignal that controls the start and the end of a 1 H shift operation ofthe source driver 300. By performing this operation, the digital pixelsignal DA is distributed to a predetermined number (for example, 4, 6,12, or the like) of output selection paths. For example, in the case ofsix-selector mode, a predetermined number (s/6) of pixel signals aresimultaneously output for each six source lines SL, and this operationis repeated a total of six times, whereby pixel signals of 1 H periodare discharged.

The short circuit control signal Csh is a signal that is used for dotinversion. The short circuit control signal Csh is generated by thedisplay control circuit 200 based on the horizontal synchronizationsignal HSY and the control signal Dc and is output to the source driver300.

The display control circuit 200 generates the gate start pulse signalGSP, the gate clock signal GCK, and the gate driver output enable signalGOE and outputs the generated signals to the gate driver 400.

The gate clock signal GCK is generated based on the horizontalsynchronization signal HSY and is used as a scanning clock for shiftingthe gate pulse of the gate driver 400.

The gate start pulse signal GSP is a signal that is in the level H for apredetermined period of one frame period (one vertical scanning period)based on the vertical synchronization signal VSY.

The gate driver output enable signal GOE is generated based on thehorizontal synchronization signal HSY and the control signal Dc. Thegate driver 400 controls the start and the end of a one frame (1F)display operation based on the gate driver output enable signal GOE andthe gate start pulse signal GSP.

The source driver 300 sequentially generates data signals as analogvoltages corresponding to pixel values for each horizontal scanning lineof an image represented by the digital pixel signal DA for each onehorizontal scanning period based on the digital pixel signal DA, thestart pulse signal SSP, and the clock signal SCK. Then, the sourcedriver outputs the generated data signals to the source lines SL1 toSLs, for example, in the six-selector mode.

In addition, the source driver 300 has a function such as dot inversionfor inverting the polarity of a pixel signal, for example, with respectto the common electric potential Vcom used as the center. Here, the “dotinversion” indicates an operation of inverting a voltage applied to theliquid crystal layer 6 for each one gate line in the direction x and foreach one source line in the direction y within one frame period byinverting the polarity of the pixel signal. Alternatively, a case wherethe polarity of the pixel signal for a same pixel is inverted for adifferent frame period (screen display period) may be included so as tobe referred to as dot inversion driving. The source driver 300 may beconfigured to invert the pixel signal only in the direction x instead ofperforming dot inversion between pixels adjacent in both the directionsy and x.

In addition, the center electric potential that becomes the reference ofthe polarity inversion of the pixel voltage is, strictly speaking, a DClevel (an electric potential corresponding to a DC component) of a pixelsignal. The DC level does not coincide with the common electricpotential Vcom. In other words, the center electric potential of thepolarity inversion is different from the DC level of the common electricpotential Vcom by a level shift due to parasitic capacitance between thegate and the drain of the TFT of each pixel. However, in a case wherethe level shift due to the parasitic capacitance is sufficiently smallrelative to the optical threshold voltage of the liquid crystal, the DClevel of the pixel signal (data signal) can be regarded to be the sameas the DC level of the common electric potential Vcom. Accordingly,commonly, the polarity of the data signal, that is, the polarity of thevoltage applied to the source line may be regarded as being invertedwith the electric potential of the common electric potential Vcom usedas the reference.

In the sense of averaging local DC biases of the liquid crystal, it ispreferable that the polarity of the pixel signal is inverted for eachpixel for 1 H period.

In addition, in the source driver 300, in order to decrease powerconsumption, adjacent source lines are short circuited in accordancewith the short circuit control signal Csh when the polarity of the datasignal is inverted.

The gate driver 400 sequentially writes data signals into the capacitorsof the pixel electrodes 22 based on the start pulse signal GSP, theclock signal GCK, and the gate driver output enable signal GOE. At thistime, the gate driver 400 sequentially selects the gate lines GL1 toGLkm for each almost 1 H period during each period (each verticalscanning period) of the digital pixel signal DA.

Inconvenience for Case (Comparative Example) of 1 H Vcom Inversion

In this embodiment, the inversion of the common electric potential Vcomfor each 1 H period is not basically performed, and the reason is asfollows.

FIG. 5 is a plan view showing the configuration for performing matrixdriving of the pixel arrangement that is colored for each pixel by usingthe source line SL and the gate line GL.

In the example of coloring shown in FIG. 5, one color of red (R), green(G), and blue (B) is arranged for each pixel column. For example, an R1signal and an R2 signal that are red (R) pixel signals are given to thesource lines SL1 and SL4 at different timings. In addition, a G1 signaland a G2 signal that are green (G) pixel signals are given to the sourcelines SL2 and SL5 at different timings. A B1 signal and a B2 signal thatare blue (B) pixel signals are given to the source lines SL3 and SL6 atdifferent timings.

Described in more detail, the R1 signal is simultaneously given tosource lines SL of the first, the seventh, and so on including thesource line SL1 with six source lines being used as one set. Similarly,the R2 signal is simultaneously given to source lines of the 4th, the10th, and so on including the source line SL2.

In addition, the G1 signal is simultaneously given to source lines ofthe second, the eighth, and so on including the source line SL2, and theG2 signal is simultaneously given to source lines of the 5th, the 11th,and so on including the source line SL5.

Similarly, the B1 signal is simultaneously given to source lines of thethird, the ninth, and so on including the source line SL3, and the B2signal is simultaneously given to source lines of the 6th, the 12th, andso on including the source line SL6.

The pixel signals (color signals) sequentially given within a set withsix source lines SL being used as the set are applied to pixel rowscorresponding to any of the activated gate lines GL1 to GLkm. This modeis referred to as a six-selector mode.

FIGS. 6A and 6B are diagrams illustrating the common electric potentialVcom and the polarity of the pixel signal in the six-selector mode.

In the comparative example in which the 1 H Vcom inversion driving isperformed, the common electric potential Vcom that is the electricpotential of the opposing electrode (the driving electrode 43) is drivenso as to be inverted, for example, with respect to 0 V as the center foreach one horizontal period (1 H).

When the common electric potential Vcom has the positive polarity, thepixel signal is given as a negative pulse. On the other hand, when thecommon electric potential Vcom has the negative polarity, the pixelsignal is given as a positive pulse. When a same voltage value is giveneven in the case of the opposite direction of the electric field, adisplay of the same grayscale is performed in the liquid crystal layer6. In FIGS. 6A and 6B, six pulses for each 1 H period are denoted by thereference signs of the color signals shown in FIG. 5.

FIG. 7B is a diagram showing a difference in the polarities of the pixelsignal pulses in a black display (BK) and a white display (W) of thecomparative example, in which 1 H Vcom inversion driving is performed,shown in FIGS. 6A and 6B. FIG. 7A is a graph acquired by actuallymeasuring changes in the electric potential of the sensor line SNL withthe horizontal axis thereof representing time. In addition, FIGS. 8A and8B are diagrams illustrating generation of noises of electric potentialvariations in the sensor line.

FIGS. 6A and 6B described above illustrate a case where a pixel that isbrighter than a specific average has a pulse repeated during a shortperiod of the 4 H period. Thus, an example in which display ofapproximately the same grayscale is performed near the white display (W)is shown. On the other hand, as shown in FIG. 7B, for the electrostaticcapacitance in the black display (BK), the pixel signal (signal of theluminance of color) is a positive pulse acquired by inverting thepolarity of the pixel signal pulse.

In FIG. 7A, a solid line corresponds to the black display (BK), and abroken line corresponds to the white display (W). In this comparativeexample, simultaneously when the driving electrode 43 applies the commonelectric potential Vcom for display, the common electric potential Vcomthat is driven in the 1 H inversion mode is used as an AC pulse of thedetection driving voltage.

The reason for the overall attenuation of the detected electricpotential is that the sensor line SNL has wiring resistance, and thedetection circuit has resistance. It can be understood that an electricpotential difference ΔV is generated due to a difference in grayscalesat the reaching point of the attenuation at the end of the 1 H period,that is, prior to change of the common electric potential Vcom from thepositive polarity to the negative polarity. This electric potentialdifference is successive to the next common electric potential Vcom ofthe negative polarity as an initial electric potential difference.Detection of an object is to detect a change (decrease) from a highlevel before the crest value of output of the sensor line attenuatesafter the change in the polarity in accordance with approach of adetection target objet. Accordingly, the electric potential differenceΔV becomes an error component of object detection.

As shown in FIG. 7B, during the period of the next negative polarityVcom, the pulse polarities of white display and black display areinverted (see FIGS. 6A and 6B). In addition, for the same pixel, thepulse polarity is inverted even during the next 1 H period. When thewhite display is defined as generation of a “+” error component as shownin FIG. 7A, one pixel line has error of “+” during the first 1 H. On theother hand, the one pixel line has error of “−” during the next 1 H.Then, such operations are repeated.

FIG. 8A is a schematic diagram representing the polarity of the error.

FIG. 8B shows a path of the change in the electric potential of thesensor line.

As described above, the driving electrode 43 (see FIGS. 1A to 1D) isdisposed so as to intersect with the source lines SL1 to SLkm.Accordingly, the driving electrode 43 and the source lines arecapacitively coupled with each other more or less. The force of thecapacitive coupling increases as the thickness of the display device isdecreased. The coupled capacitance C1 to C6 shown in FIG. 8A representsthe electrically coupled forces of the source lines SL1 to SL6 with thedriving electrode (opposing electrode) 43.

On the other hand, the driving electrode 43 is electrically coupled withthe sensor line SNL, which is disposed perpendicular thereto, throughelectrostatic capacitance Cs. Accordingly, when the electric potentialsof the source lines SL1 to SLkm are changed in accordance withapplication of a pixel signal pulse, the changed electric potentials aretransferred to the sensor line SNL from the driving electrode 43 throughthe electrostatic capacitance.

Control of Inversion of Pixel Signal for Preventing Inconvenience ofComparative Example

In order to prevent the above-described inconveniences, in thisembodiment, the following countermeasures are taken.

FIGS. 9A and 9B represent a common electric potential Vcom and a pixelsignal according to this embodiment.

In this embodiment, during the 1 H display period, the common electricpotential Vcom is maintained at a constant electric potential. As a casesatisfying this condition, there is a case where the common electricpotential Vcom is maintained at a constant electric potential even whenthe 1 H display period transits to the next 1 H display period unlessdetection driving is performed. In addition, a case where inversiondriving is performed for each 1 H also satisfies the condition. In otherwords, the period during which the common electric potential Vcom ismaintained at a constant electric potential is “at least during the 1 Hperiod”, and the common electric potential is arbitrary during otherperiods.

In addition, regarding the pulses of pixel signals, during the 1 Hdisplay period, the polarities of pulses of one or more pixel signalsare inverted with respect to those of pulses of other pixel signals. Itis preferable that the number of pulses of which the polarities areinverted is the same as that of pulses of which the polarities are notinverted, within the 1 H period. When the polarity of at least one pulseis inverted, the noise component of the output of the sensor detectionis decreased as much. However, when the number of the pulses of whichthe polarities are inverted is the same as that of the pulses of whichthe polarities are not inverted, the noise component is furtherdecreased or the noise component is scarcely generated.

Such control of the polarities of pulses is performed by controlling aninternal inversion driving unit in accordance with a short circuitcontrol signal Csh that is output from the display control unit 200 orthe like by using the source driver 300 shown in FIG. 4.

FIGS. 10A and 10B are diagrams illustrating the effect of a case wherethe polarities of the pixel signals are alternately changed in thehorizontal direction, similarly to the case of FIG. 9B.

As can be known from the example shown in FIGS. 7A and 7B, since thewhite display (W) of the negative polarity is a factor causing error of“+”, the polarity of the pixel signal and the opposite polarity becomepotential error factors. Accordingly, in the control of the pulsepolarities shown in FIG. 9B, the polarities of the potential errorfactors exist in the order of “+”, “−”, “+”, . . . for the first pixelline.

In the configuration shown in FIGS. 1A to 1D, the driving electrodes 43are thinly separated for each pixel line, and intersect with any sourceline among the s source lines SL1 to SLs in the same manner.Accordingly, as shown in FIGS. 10A and 10B, when the error component of“+” and the error component of “−” are balanced in a pixel line arrangedin the horizontal direction, the changes in the electric potentialsthrough the coupling capacitance C1 to C6 are almost canceled for thedriving electrode 43 located in any position. Therefore, the change inthe electric potential of the driving electrode 43 is sufficientlysuppressed. As a result, the change in the electric potential due to thepixel signal of the sensor line SNL is prevented or sufficientlysuppressed.

2. Second Embodiment

In the above-described first embodiment, as a premise for not generatinga noise component, there is a case where pulses having the positivepolarity and pulses having the negative polarity are balanced in thecrest values thereof. As such a case, there is a case where a specificcolor is displayed in the entire area of a horizontal pixel row or thelike. However, it is predicted that the effect of noise generationchanges depending on the content of display.

This second embodiment provides a configuration capable of acquiring ahigh effect of noise prevention regardless of the content of display asan example.

FIGS. 11A and 11B illustrate a common electric potential Vcom and apixel signal according to this embodiment.

In this embodiment, similarly to the first embodiment, the commonelectric potential Vcom is set to a fixed electric potential duringdisplay control. In addition, a preferred condition that the number ofpulses of which the polarities are inverted is the same as that ofpulses of which the polarities are not inverted within 1 H period issatisfied.

FIG. 11B representing this embodiment is different from FIG. 9A in thattwo pulses of pixel signals are simultaneously applied to a same pixelline.

At this time, in a case where one pixel of a pixel line has an ordinaryone pixel configuration shown in FIGS. 6A and 6B, pixel signals havingdifferent polarities are offset from each other.

Thus, according to this embodiment, it is necessary that a pixelconfiguration in which pixel signals having different polarities are notoffset from each other is used. This can be implemented by respectivelyarranging a pixel electrode 22 and a TFT 23 in two areas within onepixel by using technology so-called “pixel division”. The pixel divisionis based on a concept that a pixel is defined as a minimum unitdisplaying a same grayscale and a same color. In a case such a conceptis not employed, the above-described technology can be described as“technology (hereinafter, referred to as pixel-pair driving”) ofsimultaneously driving two pixels of a same color with a same grayscale.

The two areas (or two pixels forming a pixel pair), as shown in FIG. 12,may be configured as areas (or pixels) adjacent in the row direction orareas (or pixels) adjacent in the column direction. These adjacent areas(or adjacent pixels) are colored by the color filters 42 of a samecolor.

For the case of the adjacent areas (or pixels) for the row direction,two different source lines SL that are adjacent to each other aresimultaneously driven as a pair with pixel signals of a same grayscale.On the other hand, for the case of the adjacent areas (or pixels) forthe column direction, two adjacent gate lines GL are almostsimultaneously driven, so that a pixel signal of one source line issimultaneously written into two areas (two pixels).

Here, when described as “simultaneously”, it means that control isperformed in a substantially same period, and a slight time different isallowed.

According to the second embodiment, generation of error is prevented.Accordingly, a high effect of noise suppression can be acquiredregardless of the content of display.

In addition, as methods of controlling the pixel signal control unitshown in FIG. 4, that is, the display control circuit 200, the sourcedriver 300, and the gate driver 400, there are two methods describedbelow.

In a first method, in a case where two areas (or two pixels) for thecolumn direction (direction y) shown in FIG. 12 are driven as one pixel,it is necessary that pixel signals having different polarities areloaded into two areas (or two pixels). In such a case, a pulse havingthe positive polarity and a pulse having the negative polarity arealternately applied in the pixel signal, and the sampling timing of thepulse is controlled to be the timing when the TFT 23 is turned on by thedisplay control circuit 200 and the gate driver 400.

In such a case, the variations of the electric potential of the pixelsignal are averaged, whereby generation of noises is suppressed by thegeneration source.

In a second method, in a case where the two areas (or two pixels) forthe row direction (direction x) shown in FIG. 12 are driven as onepixel, the sampling timing of the pixel signal is not significantlyimportant. On the other hand, it is important that pixel signal pulseshaving different polarities are discharged to different pixel signallines at the same time. In other words, it is important that thedischarge timings of particularly the display control circuit 200 andthe source driver 300 of the pixel signal control unit for the pixelsignal lines are uniform (at the same time) in adjacent pixel signalpulses having opposite polarities. Here, “at the same time” is not forthe purpose of excluding a slight time difference.

Accordingly, although it is difficult to suppress the variations of theelectric potential of an individual pixel signal line, the variations ofthe electric potential are offset by the driving electrode 43, so thatthe influence thereof on the precision of the sensor detection can beexcluded in advance.

3. Modified Examples

In FIGS. 9A and 9B, the R1 signal, the R2 signal, the G1 signal, the G2signal, the B1 signal, and the B2 signal are supplied to (s/6) pixelsignal lines (source lines SL) as pixel signal pulses having a samepolarity. By changing the selector mode, for example, by simultaneouslysupplying halves of the R1 signal and the R2 signal and simultaneouslysupplying the remaining halves thereof, noises that are temporallyoverlapped in the driving electrode 43 can be offset from each other. Insuch a case, although the variations of the electric potential in eachsource line SL are not suppressed, the noises have different polaritiesand thus are offset from each other in the driving electrode 43. As aresult, overlapping between noises in the sensor line SNL is preventedor suppressed.

In the second embodiment, it can be configured that the source driver300 shown in FIG. 4 can switch between a pixel division mode in whichthe precision of sensor detection has priority and a common mode inwhich high-quality image display has priority by not performing pixeldivision.

For example, an operation screen is displayed. Then, in a case where anoperation through touch detection that is performed by a finger or thelike is expected, the pixel division mode may be set so as to increasethe precision of sensor detection. On the other hand, in other caseswhere a video is reproduced or the like, the pixel division mode may bereleased so as to perform high-quality video display.

FIGS. 13 to 15 represent examples of the structure of the opposingsubstrate side 4 of a horizontal electric field mode liquid crystaldisplay device.

As described above, in the horizontal electric field mode, a pixelelectrode 22 and a driving electrode 43 are disposed on a drivingsubstrate 2 side.

In the structure shown in FIG. 13, the driving electrode 43 is disposedon the front-side (display surface side) face of a TFT substrate 21, andthe driving electrode 43 and a pixel electrode 22 are located adjacentto each other through an insulating layer 24. The driving electrode 43is disposed in a line shape elongated in the direction of a display line(direction x), and the pixel electrodes 22 are separated for each pixelin the direction of the display line.

The TFT substrate 21 is bonded to the glass substrate 41 with the pixelelectrode 22 side thereof being located adjacent to a liquid crystallayer 6. The liquid crystal layer 6 is strongly maintained by a spacernot shown in the figure.

Reference numeral “49” denotes a base member of the display surface sidesuch as glass or a transparent film. On one face of the base member 49,the sensor line SNL is formed. The sensor line SNL maintained in thebase member 49 is fixed to the anti-liquid crystal side surface of theglass substrate 41 through an adhesive layer 48.

On the other hand, to the rear surface of the TFT substrate 21, a firstpolarizing plate 61 is attached, and a second polarizing plate 62 havingthe polarization direction different from that of the first polarizingplate 61 is attached to the display surface side of the base member 49.

On the display surface side of the second polarizing plate 62, aprotection layer not shown in the figure is formed.

In the structure shown in FIG. 14, a color filter 42 is formed on theliquid crystal side of the glass substrate 41 in advance. In the colorfilter 42, color areas that are different for each (sub) pixel areregularly disposed.

In the structure shown in FIG. 15, the laminated structure on thedisplay surface side is different from that of FIG. 14.

In the structure shown in FIG. 14, the sensor line SNL is formed in thebase member 49 in advance and is attached, for example, as a roll-shapedmember. However, in FIG. 15, the sensor line SNL is formed on thedisplay surface side of the glass substrate 41, and the secondpolarizing plate 62 is attached thereon.

According to the first and second embodiments and the modified examplesdescribed above, the thickness of the display device can be decreased bydisposing the detection electrode used for noise detection near thedisplay functional layer. In such a case, the noise caused by the pixelsignal can be decreased. Accordingly, a touch panel-attached displaydevice having improved detection precision can be provided.

In particular, when pixels of which the polarities are inverted areadjacently located, a display device capable of preventing generation offlicker or the like together with improving the precision of touchdetection can be achieved.

In addition, by employing dot-inversion driving, a signal of which thepolarity is inverted can be written in an easy manner.

In addition, by configuring a liquid crystal display device, detectiondriving and display driving can be controlled by an electrode (commonelectrode) of one layer. Accordingly, an integrated display device canbe formed.

In the horizontal electric field mode, the common electrode can beformed on the TFT side. Accordingly, a driving circuit that is used fordriving the common electrode as an electrode for a touch panel can beformed in an easy manner.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope and without diminishing itsintended advantages. It is therefore intended that such changes andmodifications be covered by the appended claims.

The application is claimed as follows:
 1. A display device comprising: adisplay functional layer that can change display for each pixel inaccordance with an application voltage; a plurality of drivingelectrodes, disposed in a first direction so as to be separated from oneanother, to which a display reference electric potential maintained at aconstant level is applied during a display period in which display isperformed in a pixel arrangement along the first direction and to whicha detection driving signal is applied when detection scanning isperformed by changing the display reference electric potential toanother electric potential; a plurality of pixel signal lines to whichpixel signals used for applying the application voltage to the displayfunctional layer in accordance with an electric potential differencefrom the display reference electric potential are applied; a pluralityof detection electrodes that are disposed so as to be separated from oneanother in a direction other than the first direction, are coupled withthe plurality of the driving electrodes as electrostatic capacitance,generate detection electric potentials in response to the detectiondriving signal that is applied to at least one driving electrode; and apixel signal control unit that controls the plurality of pixel signalsapplied to the plurality of pixel signal lines so that pixel signals inone display period have at least one pulse whose polarity is invertedand that the pixel signals before being inverted and the pixel signalsafter being inverted have the same electric potential differences as thedisplay reference electric potential.
 2. The display device according toclaim 1, wherein the inside of one pixel is divided into two areas, anda pixel electrode and a switching device are disposed in the areas, andwherein the pixel signal control unit controls polarity control andsupply timings of the pixel signals and opening or closing of theswitching device such that the same pixel signal is supplied from onepixel signal line to the two areas inside the same pixel with oppositepolarities.
 3. The display device according to claim 1, wherein theinside of one pixel is divided into two areas, and each of the areas isconfigured so as to be able to maintain different pixel signals, andwherein the pixel signal control unit controls polarity control of thepixel signals and discharge timings for two different pixel signal linesadjacent to each other such that the same pixel signal is supplied fromthe two different pixel signal lines to the two areas inside the samepixel with opposite polarities.
 4. The display device according to claim1, wherein the pixel signal control unit controls the pixel signalshaving opposite polarities so as to be simultaneously discharged to aplurality of pixel signal lines when an operation of supplying the pixelsignal to one pixel electrode inside one pixel through a switchingdevice is performed for a plurality of pixels in a parallel manner. 5.The display device according to claim 1, wherein the pixel signalcontrol unit controls the number of the pixel signals having thepositive polarity with respect to a center electric potential to be thesame as the number of the pixel signals having the negative polaritywith respect to the center electric potential within the fixed displayperiod.
 6. The display device according to claim 1, wherein the pixelsignal control unit controls the polarities of the pixel signals ofadjacent pixels so as to be inverted within the fixed display period. 7.The display device according to claim 6, wherein the pixel signalcontrol unit controls the polarities of the pixel signals that areadjacent to each other in a row direction and a column direction so asto be inverted between the fixed display period and another fixeddisplay period next thereto.
 8. The display device according to claim 7,wherein the pixel signal control unit controls dot-inversion driving inwhich the polarity of the pixel signal of the same pixel is invertedbetween a display period of one screen and a display period of anotherscreen next thereto.
 9. The display device according to claim 1, whereinthe display functional layer is a liquid crystal layer.
 10. The displaydevice according to claim 1, wherein the plurality of detectionelectrodes are disposed on a display surface side of the displayfunctional layer, wherein the plurality of driving electrodes aredisposed on a side of the display functional layer that is opposite tothe display surface, and wherein a plurality of pixel electrodes,separated for each pixel, that apply the application voltage to thedisplay functional layer with respect to an electric potential of acorresponding driving electrode used as a reference for each pixel whenthe pixel signal is supplied are disposed between the display functionallayer and the plurality of driving electrodes.
 11. The display deviceaccording to claim 1, wherein the number of the inverted pulses is equalto the number of not-inverted pulses.
 12. The display device accordingto claim 1, wherein the pixel signal control unit is configured tocontrol the plurality of pixel signals applied to the plurality of pixelsignal lines so that pixel signals in 1 H display period have at leastone pulse whose polarity is inverted with respect to the displayreference electric potential from another pulse in the 1 H displayperiod, while the display reference electric potential is maintained atthe constant level in the 1 H display period.
 13. The display deviceaccording to claim 12, wherein the detection scanning is performed in aperiod that is different from the 1 H display period.
 14. The displaydevice according to claim 1, wherein two pulses of pixel signals, whichinclude a pixel signal before being inverted and a pixel signal afterbeing inverted, are simultaneously applied to a same pixel signal line.